<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Arc Shape</title>
<style>
  .bb{
		width: 100%;
		height: 140px;
		position: relative;
		z-index: -1;
		overflow: hidden;
	}

	.bb::after {
		content: '';
		width: 120%;
		height: 100px;
		position: absolute;
		left: -10%;
		top: 0;
		z-index: -1;
		border-radius: 0 0 60% 60%;
		background: #1496f1;
	}
	
</style>
</head>
<body>
<div class="bb"></div>
</body>
</html>